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Disclaimer: This calculator provides estimates only. Actual BAC varies by individual. Never use a calculator to decide if you are safe to drive — if you have consumed alcohol, do not drive.

BAC Calculator

Estimate blood alcohol content with the Widmark formula

Results are estimates for informational purposes only — not professional financial, medical, or legal advice. See how we build and verify our calculators.

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Frequently Asked Questions

What is a standard drink?

A standard drink in the US contains 14 grams of pure alcohol: 12 oz regular beer (5%), 5 oz wine (12%), or 1.5 oz distilled spirits (40%). A pint of strong craft beer may count as 1.5–2 standard drinks.

How does the body metabolize alcohol?

The liver metabolizes about 0.015% BAC per hour (roughly one standard drink per hour for an average person). This rate is fairly constant — coffee, food, exercise, or water cannot speed it up significantly.

Why do women have higher BAC than men at the same intake?

Women generally have a lower ratio of body water to total weight (55% vs 68% for men). Since alcohol distributes through body water, less dilution means higher BAC. This is the "r" factor in the Widmark formula.

What BAC is legal for driving in the US?

The US federal limit is 0.08% BAC. At 0.08%, driving risk doubles compared to 0.00%. At 0.05% (the legal limit in many countries), reaction time and judgment are already measurably impaired.

Is this calculator accurate?

The Widmark formula gives an estimate. Individual metabolism varies by up to ±30%. Factors like food consumption, medications, liver health, and tolerance affect actual BAC. Only a breathalyzer or blood test gives a precise reading.

BAC Impairment Levels

0.02–0.05%

Mild relaxation, slight warming

0.05–0.08%

Reduced coordination, impaired judgment

0.08%

US legal limit for driving

0.08–0.15%

Slurred speech, poor balance

0.15–0.25%

Confusion, nausea, vomiting

0.25%+

Blackout risk, alcohol poisoning

Standard Drink Equivalents

Regular beer (12 oz, 5%)1 drink
Wine (5 oz, 12%)1 drink
Spirits (1.5 oz, 40%)1 drink
Craft IPA pint (8%)~1.5 drinks
Hard seltzer (12 oz, 5%)1 drink

How BAC Is Calculated (Widmark Formula)

The Widmark formula is the standard method used by law enforcement and medical professionals to estimate BAC:

BAC = (alcohol grams ÷ (body weight grams × r)) × 100

Current BAC = Peak BAC − (0.015 × hours elapsed)

r = body water constant (0.68 for men, 0.55 for women) | 1 standard drink = 14g pure alcohol

Legal BAC Limits Around the World

Country / RegionLegal Limit
United States0.08%
United Kingdom0.08% (0.05% in Scotland)
European Union (most)0.05%
Germany0.05% (0.00% for new drivers)
Japan0.03%
Sweden / Poland0.02%